Ultrasonic scalers are used in dental offices for de-plaqueing teeth. Unlike manual scalers, these instruments are powered i.e., the tip of the instrument vibrates at an ultrasonic frequency allowing quick and easy debridement. The operator has less hand fatigue as most of the energy for removing the plaque comes from the generator that powers the instrument. The dental practitioner need only lightly touch the tip of the instrument at an angle to the tooth surface to dislodge the plaque.
Known ultrasonic scalers, such as scaler 10 illustrated in FIG. 1A, have a handpiece 12a coupled at one end 12a-1 to a cable 12b which includes a hose, to provide a fluid, and conductors to provide electrical energy. The other end of the cable 12b terminates at an electrical generator and fluid source 12c. One type of fluid is water.
The other end of the handpiece 12a-2 is hollow and is intended to receive a replaceable insert 14 with a transducer 14a (magnetostrictive or piezoelectric) carried on the insert. The transducer 14a extends from a proximal end of the insert 14 into the hollow body 12a-2. An ultrasonically vibrated tip 14b extends from a distal end of the insert. One such insert has been disclosed and claimed in U.S. Pat. No. 5,775,901, entitled “Insert For Ultrasonic Scaler”, incorporated herein by reference.
Known magnetostrictive ultrasonic inserts function by exciting a stack of thin nickel plates at a frequency equal to the stack's natural frequency. The excitation is induced through an electrical generator in unit 12c, which supplies a current to a coil embedded in the handpiece. When the insert 14 is placed in the handpiece 12a and the frequency generator 12c is powered on, the operator tunes the generator (manual tuning) until it reaches the resonance frequency i.e., attains the natural frequency of the insert. Alternately, auto-tune units automatically lock on the insert resonance frequency once powered on. At this time, the stack starts vibrating. This vibration of the stack is amplified and transmitted to the tip 12b by means of a connecting body or concentrator. The connecting body is made from material that provides good sound transmission efficiency.
While the insert 14 is operational, fluid is pumped through the cable-generator system 12b, c and through the handpiece 12a to the tip 14b of the insert 14. The vibrating tip 14b breaks the fluid stream into a spray. The spray not only keeps the tip cool, but also keeps the surface of the tooth cool and provides protection against tissue damage.
The fluid path through the handpiece 12a needs to be sealed such that no leakage occurs until the fluid stream exits from the insert at the very tip through a fluid delivery channel. Typically, ultrasonic inserts do not have any moving parts other than the minuscule displacement of the nickel stack, the connecting body or the tip.
Known magnetostrictive dental scaling ultrasonic inserts used in the U.S.A. are designed to vibrate at 25 kHz or 30 kHz frequencies. Another system, popular in Europe, uses a piezoelectric transducer.
In using an ultrasonic scaler during a cleaning, the dental practitioner will need to repeatedly re-orient the location of the insert tip 14b with respect to tooth surface depending on which tooth of the mouth is being cleaned. In making this angular adjustment, as illustrated in FIG. 1B, the practitioner will typically take the insert out of the patient's mouth, rotate the insert 14, and tip 14b, inside the handpiece 12a locating tip 14b at a desired angular position. Both hands are used for this rotation as the frictional forces that produce a tight fit of the insert 14 in handpiece 12a must be overcome. During a typical treatment, the process of reorienting the tip must be carried out numerous times. This is not only time consuming but also interrupts the ease and smooth flow of work.
In areas of the mouth where the practitioner chooses not to rotate the insert 14, the practitioner's wrist must be twisted sufficiently to achieve the same function. This twisting action is opposed by the resistance of the cable 12b, the fluid supply hose and power conductors, which is attached to the handpiece 12a. 
There continues to be a need for ultrasonic scalers which are more comfortable and less fatiguing to use than known instruments. Preferably, any improvements will be downwardly compatible with the numerous generators and handpieces that are already present in dental offices.